Communication method, terminal, and base station

Abstract

Embodiments provide a communication method, terminal, and a base station. The method includes: receiving, by terminal, a reference signal sent by a base station; and obtaining, by the terminal, channel energy of a narrow beam by measuring the reference signal, where the narrow beam is a directional beam. According to the communication method in the embodiments of the present disclosure, the terminal may obtain the channel energy of the narrow beam by measuring the reference signal. Compared with the prior art in which channel energy of a narrow beam is measured on a base station side, a difference is that the terminal can more accurately estimate the channel energy of the narrow beam. That is, the channel energy of the narrow beam estimated by the terminal can more accurately reflect channel quality, and transmission efficiency can be improved.

What is claimed is: 
     
       1. A communication method, comprising:
 receiving, by a terminal, a reference signal sent by a base station; and 
 obtaining, by the terminal, channel energy of a narrow beam by measuring the reference signal, wherein the narrow beam is a directional beam; 
 obtaining, by the terminal, channel energy of a wide beam by measuring an unweighted cell-specific reference signal (CRS) or an unweighted channel state information reference signal (CSI-RS); and 
 obtaining, by the terminal, a beam gain, wherein the beam gain is a ratio of the channel energy of the narrow beam to the channel energy of the wide beam. 
 
     
     
       2. The method according to  claim 1 , wherein the reference signal is a demodulation reference signal (DMRS). 
     
     
       3. The method according to  claim 1 , wherein:
 receiving, by a terminal, a reference signal sent by a base station comprises:
 receiving, by the terminal, channel state information reference signals (CSI-RS)s that are sent by the base station by using N CSI-RS ports and that are respectively weighted by using N weight values, wherein:
 the N CSI-RS ports correspond one-to-one to the N weight values, 
 the N weight values are different from each other; and 
 the N weight values correspond one-to-one to beams in N directions; and 
 
 
 obtaining, by the terminal, channel energy of a narrow beam by measuring the reference signal comprises:
 obtaining, by the terminal, channel energy of N first beams by measuring the CSI-RSs that are weighted by using the N weight values; and 
 determining, by the terminal, a channel energy with a largest value in the channel energies of the N first beams as the channel energy of the narrow beam. 
 
 
     
     
       4. The method according to  claim 1 , wherein:
 receiving, by terminal, a reference signal sent by a base station comprises:
 receiving, by the terminal, an unweighted cell-specific reference signal (CRS) and/or an unweighted channel state information reference signal (CSI-RS) transmitted by the base station by using each antenna; and 
 
 obtaining, by the terminal, channel energy of a narrow beam by measuring the reference signal comprises:
 obtaining, by the terminal, a channel estimation value of each antenna by measuring the unweighted CRS and/or the unweighted CSI-RS; 
 obtaining, by the terminal by performing a multiplication operation on the channel estimation values and each of M weight values in a preset codebook, channel energy of M second beams that correspond one-to-one to the M weight values; and 
 determining, by the terminal, a channel energy with a largest value in the channel energies of the M second beams as the channel energy of the narrow beam. 
 
 
     
     
       5. The method according to  claim 1 , further comprising:
 reporting, by the terminal, a beam gain (D1) event to the base station, wherein the beam gain (D1) event indicates that the beam gain is greater than a first preset threshold. 
 
     
     
       6. The method according to  claim 1 , wherein:
 reporting, by the terminal, a beam gain (D1) event to the base station, wherein the beam gain (D1) event indicates that the beam gain is greater than a first preset threshold. 
 
     
     
       7. The method according to  claim 1 , wherein:
 reporting, by the terminal, a first event to the base station when the beam gain satisfies that a duration of an entry condition of a first event is greater than a first time to trigger (TTT), wherein:
 the first TTT is a preconfigured TTT; and 
 the entry condition of the first event is determined by the terminal based on the beam gain. 
 
 
     
     
       8. A communication method, comprising:
 receiving, by a source base station, a gain event reported by a terminal, wherein:
 the gain event indicates that a beam gain of a serving cell is greater than a preset threshold; 
 the source base station is a base station of the serving cell; 
 the beam gain of the serving cell is a ratio of channel energy of a narrow beam of the serving cell to channel energy of a wide beam of the serving cell; and 
 the narrow beam of the serving cell is a directional beam. 
 
 
     
     
       9. The method according to  claim 8 , further comprising:
 receiving, by the source base station, a measurement report (A3) event reported by the terminal; and 
 sending, by the source base station, a handover command to the terminal after a preset time period based on the measurement report (A3) event, to control handover of the terminal from the serving cell to a target cell. 
 
     
     
       10. The method according to  claim 9 , wherein an entry condition of the measurement report (A3) event is determined by the terminal based on the beam gain. 
     
     
       11. The method according to  claim 8 , further comprising:
 communicating, by the source base station, with the terminal by using a first beamforming communication mode in a process of handover of the terminal from the serving cell to a target cell, wherein the serving cell is neighboring to the target cell. 
 
     
     
       12. The method according to  claim 11 , wherein:
 before sending, by the source base station, a handover command to the terminal, the method further comprises:
 receiving, by the source base station, a first identifier sent by the terminal, wherein:
 the first identifier is used to indicate a first channel state information reference signal (CSI-RS) port corresponding to the source base station; and 
 the first CSI-RS port corresponds to the channel energy of the narrow beam of the serving cell; and 
 
 
 before communicating, by the source base station, with the terminal by using a first beamforming communication mode, the method further comprises:
 determining, by the source base station, the first beamforming communication mode based on the first identifier. 
 
 
     
     
       13. The method according to  claim 11 , wherein:
 before sending, by the source base station, a handover command to the terminal, the method further comprises:
 receiving, by the source base station, a second identifier sent by the terminal, wherein:
 the second identifier is used to indicate a first codebook index; and 
 the first codebook index corresponds to the channel energy of the narrow beam of the serving cell; and 
 
 
 before communicating, by the source base station, with the terminal by using a first beamforming communication mode, the method further comprises:
 determining, by the source base station, the first beamforming communication mode based on the second identifier. 
 
 
     
     
       14. A terminal, comprising:
 a transceiver, configured to receive a reference signal sent by a base station; and 
 a processor, configured to:
 obtain channel energy of a narrow beam by measuring the reference signal received by the transceiver, wherein the narrow beam is a directional beam; 
 obtain channel energy of a wide beam by measuring an unweighted cell-specific reference signal (CRS) or an unweighted channel state information reference signal (CSI-RS); and 
 obtain a beam gain, wherein the beam gain is a ratio of the channel energy of the narrow beam to the channel energy of the wide beam. 
 
 
     
     
       15. The terminal according to  claim 14 , wherein the reference signal is a demodulation reference signal (DMRS). 
     
     
       16. The terminal according to  claim 14 , wherein:
 the transceiver is configured to:
 receive channel state information reference signals (CSI-RSs) that are sent by the base station by using N CSI-RS ports and that are respectively weighted by using N weight values, wherein:
 the N CSI-RS ports correspond one-to-one to the N weight values, the N weight values are different from each other; and 
 the N weight values correspond one-to-one to beams in N directions; and 
 
 
 the processor is configured to:
 obtain channel energy of N first beams by measuring the CSI-RSs that are weighted by using the N weight values; and 
 determine a channel energy with a largest value in the channel energies of the N first beams as the channel energy of the narrow beam. 
 
 
     
     
       17. The terminal according to  claim 14 , wherein:
 the transceiver is configured to:
 receive an unweighted cell-specific reference signal (CRS) and/or an unweighted channel state information reference signal (CSI-RS) that are/is transmitted by the base station by using each antenna; and 
 
 the processor is configured to:
 obtain a channel estimation value of each antenna by measuring the unweighted CRS and/or the unweighted CSI-RS; 
 obtain, by performing a multiplication operation on the channel estimation values and each of M weight values in a preset codebook, channel energy of M second beams that correspond one-to-one to the M weight values; and 
 determine a channel energy with a largest value in the channel energies of the M second beams as the channel energy of the narrow beam. 
 
 
     
     
       18. The terminal according to  claim 14 , wherein the transceiver is further configured to:
 report a beam gain (D1) event to the base station, wherein the beam gain (D1) event indicates that the beam gain is greater than a first preset threshold. 
 
     
     
       19. The terminal according to  claim 14 , wherein the transceiver is further configured to:
 when the beam gain satisfies that duration of an entry condition of a first event is greater than a first time to trigger (TTT), report the first event to the base station, wherein:
 the first TTT is a preconfigured TTT; and 
 the entry condition of the first event is determined by the terminal based on the beam gain. 
 
 
     
     
       20. The terminal according to  claim 14 , wherein the transceiver is further configured to:
 when the beam gain satisfies that a duration of an entry condition of a measurement report (A3) event is greater than a second time to trigger (TTT), report the measurement report (A3) event to the base station, wherein the second TTT is a product of a beam gain scale factor and a preconfigured TTT, and the beam gain scale factor corresponds to the beam gain.